The present invention relates to an image forming apparatus of a copying machine having a function of serial page copy (book-copy function).
When copying pages of a book on a single page at a time basis, a page to be copied in the book needs to be moved for each page copying, which is sometimes inconvenient, especially when the number of pages to be copied is large or the book is thick. In order to overcome this inconvenience, there has been developed a copying machine having a function of serial page copying wherein an optical system scans successively each of two pages in a spread of the book and thereby two pages in the spread can be copied automatically without the necessity of moving the book.
When a key for serial page copy on the aforesaid copying machine is pressed for the serial page copy, the copying machine detects whether the paper size selected in it is either A4 or B5, and if it is A4 or B5, a display lamp indicating that the serial page copy is ready is lit and the serial page copy is performed after a copy key is pressed.
On the conventional copying machine mentioned above, the serial page copy can be performed only when the selected paper (cassette) size is detected to be the size of A4 or B5. The basis for this is that the positions for both first page 130 and second page 140 of a document accord with the position of an image-transfer paper as shown in FIGS. 7 (a) and (b) in this case, and thereby the independent copying for the first page and that for the second page can be performed in series through the respective scannings (shown with arrows in the figure) of an optical system. In the manual feed mode, there is no means for detecting paper size due to the mechanism of the apparatus, and thus it is impossible to recognize the size, which makes the serial page copy impossible to perform. Thus, the serial page copy in the manual feeding mode has been impossible despite the actual image-transfer paper size of A4 or B5. There has been, therefore, a problem of a narrow range for the application of serial page copy.
When cassettes in R-series such as A4R and B5R are used, the positions of both first page 130 and second page 140 of a document do not accord with the position of transfer paper 121 (shown with dotted lines in FIG. 7 (c)) and the document and the transfer paper do not agree in terms of their longitudinal and lateral directions and thereby the page serial copy can not be performed.
Further, users are generally using cassettes of an 'R series such as A4R or B5R, and when users having no cassettes of the size of A4 and B5 make copies in a serial page copy mode, they need to buy cassettes of A4 and B5, which is inconvenient for users.
Furthermore, it is also considered that the serial page copy for the papers which are neither of an A4 size nor of a B5 size is requested by users.